Is there any limitation when using a device on the ground?

Using a gate on  the ground is useful in the folowing instances

In a three ppoint start when you want to start on hand-lift

1. In a  standing two point start where you want to start on foot-lift
2. In a 5-10-5 test or similar where you want to measure splits as foot or hand touches a line
3. Limitations exist in the following paradigms

A gate on the groung makes a poor wifi access point  see What is the Maximum Distance between iPad and the Access point Timing gate?

Generally an UNO device is used for Sensing on the ground, because

It’s laser sensor is lower than a dual beam gate (You would need to disable the top beam in a dual beam gate)

It is more stable, particularly if the magnetic ground palte accessories are used.